Electromagnetic pump

ABSTRACT

An electromagnetic pump including a pump portion that includes a cylinder that is formed with an intake port and a discharge port that are in communication with a flow passage of a fluid pressure circuit, a pin groove, and a piston that through a reciprocal movement inside the cylinder suctions a fluid from the intake port and discharges the fluid from the discharge port; and an electromagnetic portion that reciprocates the piston. Inserting the pump portion inside a fluid pressure circuit with the electromagnetic portion externally exposed from the fluid pressure circuit, and inserting a pin from outside into the pin groove incorporates the electromagnetic pump inside a fluid pressure circuit, and the pin groove is formed at a position farther from an electromagnetic portion side than the discharge port.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2011-068805 filed onMar. 25, 2011 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to an electromagnetic pump including: apump portion that includes a cylinder that is formed with an intake portand a discharge port that are in communication with a flow passage of afluid pressure circuit, a pin groove, and a piston that through areciprocal movement inside the cylinder suctions a fluid from the intakeport and discharges the fluid from the discharge port; and anelectromagnetic portion that reciprocates the piston, wherein insertingthe pump portion inside the fluid pressure circuit with theelectromagnetic portion externally exposed from the fluid pressurecircuit, and inserting a pin from outside into the pin grooveincorporates the electromagnetic pump inside the fluid pressure circuit.

DESCRIPTION OF THE RELATED ART

As an electromagnetic pump of this type, related art has proposed anelectromagnetic pump that is incorporated into a hydraulic circuit(valve body) of an automatic transmission mounted in an automobile thathas an idling stop function (e.g., see Japanese Patent ApplicationPublication No. JP-A-2010-181010). The electromagnetic pump is used tomaintain a clutch of the automatic transmission to a stroke end pressurewhile an engine is stopped.

SUMMARY OF THE INVENTION

The electromagnetic pump described above is designed with a relativelyhigh discharge performance because of the need to apply a hydraulicpressure to an oil chamber of the clutch. Hydraulic fluid is thus proneto leak from the discharge port, and the discharge performance of theelectromagnetic pump may suffer as a consequence.

An electromagnetic pump of the present invention secures dischargeperformance by suppressing hydraulic fluid leakage.

The electromagnetic pump of the present invention employs the followingto achieve the above.

An electromagnetic pump according to the present invention includes: apump portion that includes a cylinder that is formed with an intake portand a discharge port that are in communication with a flow passage of afluid pressure circuit, a pin groove, and a piston that through areciprocal movement inside the cylinder suctions a fluid from the intakeport and discharges the fluid from the discharge port; and anelectromagnetic portion that reciprocates the piston. In theelectromagnetic pump, inserting the pump portion inside the fluidpressure circuit with the electromagnetic portion externally exposedfrom the fluid pressure circuit, and inserting a pin from outside intothe pin groove incorporates the electromagnetic pump inside the fluidpressure circuit. In addition, the pin groove is formed at a positionfarther from an electromagnetic portion side than the discharge port.

According to the present invention, the electromagnetic pump includes: apump portion that includes a cylinder that is formed with an intake portand a discharge port that are in communication with a flow passage of afluid pressure circuit, a pin groove, and a piston that through areciprocal movement inside the cylinder suctions a fluid from the intakeport and discharges the fluid from the discharge port; and anelectromagnetic portion that reciprocates the piston. In theelectromagnetic pump, inserting the pump portion inside the fluidpressure circuit with the electromagnetic portion externally exposedfrom the fluid pressure circuit, and inserting a pin from outside intothe pin groove incorporates the electromagnetic pump inside the fluidpressure circuit. In addition, the pin groove is formed at a positionfarther from an electromagnetic portion side than the discharge port.Since there is no leakage path from the discharge port through the pingroove to outside, hydraulic fluid leakage can thus be suppressed. As aconsequence, the discharge performance of the electromagnetic pump canbe secured.

In the electromagnetic pump described above, the intake port may beformed on an end surface of the cylinder on a side opposite from theelectromagnetic portion side, the discharge port may be formed in a sidesurface of the cylinder, and the pin groove may be formed on the sidesurface of the cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram that shows the overall configuration ofan electromagnetic pump 20 as an embodiment of the present invention;

FIG. 2 is an exterior view that shows the exterior of theelectromagnetic pump 20 of the embodiment;

FIG. 3 is a cross-sectional view that shows a cross section A-A of theelectromagnetic pump 20 in FIG. 2; and

FIG. 4 is an explanatory diagram that shows how the electromagnetic pump20 of the embodiment is attached to a valve body 80.

DETAILED DESCRIPTION OF THE EMBODIMENT

Next, an embodiment of the present invention will be described.

FIG. 1 is a structural diagram that shows the overall configuration ofan electromagnetic pump 20 as an embodiment of the present invention. Asshown in the figure, the electromagnetic pump 20 of the embodiment isconfigured as a piston pump that reciprocates a piston 50 topressure-feed a hydraulic oil. The electromagnetic pump 20 also includesa solenoid portion 30 that generates an electromagnetic force, and apump portion 40 that operates by the electromagnetic force of thesolenoid portion 30. The electromagnetic pump 20 is incorporated into avalve body 80 formed with a plurality of oil passages as a portion of ahydraulic circuit for turning on and off a clutch or a brake provided inan automatic transmission mounted in an automobile, for example.

The solenoid portion 30 has a case 31 as a bottomed cylinder member onwhich an electromagnetic coil 32, a plunger 34 as a movable element, anda core 36 as a fixed element are disposed. Applying a current to theelectromagnetic coil 32 forms a magnetic circuit in which magnetic fluxcircles the case 31, the plunger 34, and the core 36, whereby theplunger 34 is suctioned and presses out a shaft 38 that is in contactwith a proximal end of the plunger 34.

The pump portion 40 includes: a hollow cylindrical cylinder 42 that isjoined to the solenoid portion 30; the piston 50 that is slidablydisposed inside the cylinder 42, and has a base end surface that iscoaxial with and contacts a proximal end of the shaft 38 of the solenoidportion 30; a spring 46 that contacts a proximal end of the piston 50,and applies a biasing force in a direction opposite from the directionin which the solenoid portion 30 applies an electromagnetic force; anintake check valve 60 that supports the spring 46 from a side oppositefrom the proximal end surface of the piston 50, and allows the hydraulicoil to flow in the suctioning direction toward a pump chamber 41 andprohibits the hydraulic oil from flowing in the reverse direction; adischarge check valve 70 that is embedded in the piston 50, and allowsthe hydraulic oil to flow in the discharging direction from the pumpchamber 41 and prohibits the hydraulic oil from flowing in the reversedirection; a strainer 47 that is disposed upstream of the intake checkvalve 60, and catches foreign matter included in the hydraulic oil thatis suctioned toward the pump chamber 41; and a cylinder cover 48 thatcovers an opening portion 42 a on a side of the cylinder 42 oppositefrom the solenoid portion 30 with the piston 50, the discharge checkvalve 70, the spring 46, the intake check valve 60, and the strainer 47incorporated in that order from the opening portion 42 a. Spiral groovesare formed in the circumferential direction on an inner circumferentialsurface of the cylinder cover 48 and an outer circumferential surface ofthe opening portion 42 a of the cylinder 42. Threadedly fastening thecylinder cover 48 with the opening portion 42 a of the cylinder 42attaches the cylinder cover 48 to the opening portion 42 a of thecylinder 42. Note that, in the pump portion 40, an intake port 49 forsuctioning the hydraulic oil is formed at an axial center of thecylinder cover 48, and a discharge port 43 for discharging the suctionedhydraulic oil is formed in a side surface of the cylinder 42.

The piston 50 is formed from a cylindrical piston body 52, and acylindrical shaft portion 54 b that has an outer diameter smaller thanthe piston body 52 and an end surface that contacts the proximal end ofthe shaft 38 of the solenoid portion 30. The piston 50 moves inassociation with the shaft 38 of the solenoid portion 30 andreciprocates inside the cylinder 42. A cylindrical, bottomed hollowportion 52 a that can accommodate the discharge check valve 70 is formedat an axial center of the piston 50. The hollow portion 52 a of thepiston 50 runs from a proximal end surface of the piston 50 to insidethe piston body 52, and extends to partway inside the shaft portion 54.In addition, two through holes 54 a, 54 b that intersect at a 90-degreeangle in the radial direction are formed in the shaft portion 54. Thedischarge port 43 is formed around the shaft portion 54, and the hollowportion 52 a of the piston 50 is provided in communication with thedischarge port 43 through the two through holes 54 a, 54 b.

The intake check valve 60 includes: a valve body 62 that is fitted byinsertion to an inner circumferential surface of the opening portion 42a of the cylinder 42, formed therein with a bottomed hollow portion 62a, and formed with a center hole 62 b that provides communicationbetween the hollow portion 62 a and the pump chamber 41 at an axialcenter of the bottom of the hollow portion 62 a; a ball 64; a spring 66that applies a biasing force to the ball 64; and a plug 68 that isfitted by insertion to an inner circumferential surface of the hollowportion 62 a with the ball 64 and the spring 66 incorporated into thehollow portion 62 a of the valve body 62. The plug 68 is formed as aring-shaped member that includes a center hole 69 with an inner diametersmaller than the outer diameter of the ball 64. The ball 64 biased bythe spring 66 is pressed against the center hole 69.

When a differential pressure (P1-P2) between a pressure P1 on the intakeport 49 side and a pressure P2 on the pump chamber 41 side is equal toor greater than a predetermined pressure that overcomes the biasingforce of the spring 66, the spring 66 contracts and causes the ball 64to separate from the center hole 69 of the plug 68, thereby opening theintake check valve 60. When the differential pressure (P1-P2) describedabove is less than the predetermined pressure, the spring 66 elongatesand causes the ball 64 to press against the center hole 69 of the plug68, thereby blocking the center hole 69 and closing the intake checkvalve 60.

The discharge check valve 70 includes: a ball 74, a spring 76 thatapplies a biasing force to the ball 74; and a plug 78 as a ring-shapedmember that has a center hole 79 with an inner diameter smaller than theouter diameter of the ball 74. The spring 76, the ball 74, and the plug78 are incorporated in that order from an opening portion 52 b of thehollow portion 52 a of the piston 50, and fixed by a snap ring 79.

When a differential pressure (P2-P3) between the pressure P2 on the pumpchamber 41 side and a pressure P3 on the discharge port 43 side is equalto or greater than a predetermined pressure that overcomes the biasingforce of the spring 76, the spring 76 contracts and causes the ball 74to separate from the center hole 79 of the plug 78, thereby opening thedischarge check valve 70. When the differential pressure (P2-P3)described above is less than the predetermined pressure, the spring 76elongates and causes the ball 74 to press against the center hole 79 ofthe plug 78, thereby blocking the center hole 79 and closing thedischarge check valve 70.

In the cylinder 42, the pump chamber 41 is formed by a space that issurrounded by an inner wall 42 b on which the piston body 52 slides, asurface of the piston body 52 on the spring 46 side, and a surface ofthe valve body 62 of the intake check valve 60 on the spring 46 side. Inthe pump chamber 41, when the piston 50 moves by the biasing force ofthe spring 46, the volume inside the pump chamber 41 increases andcauses the intake check valve 60 to open and the discharge check valve70 to close, thereby suctioning the hydraulic oil through the intakeport 49. When the piston 50 moves by the electromagnetic force of thesolenoid portion 30, the volume inside the pump chamber 41 decreases andcauses the intake check valve 60 to close and the discharge check valve70 to open, thereby discharging the suctioned hydraulic oil through thedischarge port 43.

Also, the cylinder 42 is formed with the inner wall 42 b on which thepiston body 52 slides, and an inner wall 42 c on which the shaft portion54 slides. The inner wall 42 b and the inner wall 42 c are arranged in astepped configuration, and the discharge port 43 is formed at a steppedsection thereof. The stepped section forms a space that is surrounded bya ring-shaped surface of the stepped section between the piston body 52and the shaft portion 54, and an outer circumferential surface of theshaft portion 54. Because the space is formed on the opposite side ofthe piston body 52 from the pump chamber 41, the volume of the spacedecreases when the volume of the pump chamber 41 increases, and thevolume of the space increases when the volume of the pump chamber 41decreases. At such times, the change in the volume of the space issmaller than the change in the volume of the pump chamber 41, becausethe surface area (pressure-receiving surface area) of the piston body 52that receives pressure from the pump chamber 41 side is larger than thesurface area (pressure-receiving surface area) of the piston body 52that receives pressure from the discharge port 43 side. Therefore, thespace functions as a second pump chamber 56. In other words, when thepiston 50 moves by the electromagnetic force of the solenoid portion 30,an amount of hydraulic oil that corresponds to the difference in theamount that the volume of the pump chamber 41 decreases and the amountthat the volume of the second pump chamber 56 increases is deliveredfrom the pump chamber 41 to the second pump chamber 56 via the dischargecheck valve 70 and discharged through the discharge port 43. When thepiston 50 moves by the biasing force of the spring 46, an amount ofhydraulic oil that corresponds to the amount that the volume of the pumpchamber 41 increases is suctioned through the intake port 49 into thepump chamber 41 via the intake check valve 60, while an amount ofhydraulic oil that corresponds to the amount that the volume of thesecond pump chamber 56 decreases is discharged from the second pumpchamber 56 through the discharge port 43. Accordingly, one reciprocalmovement of the piston 50 discharges the hydraulic oil twice from thedischarge port 43, which can reduce discharge variation and improvedischarge performance.

FIG. 2 shows the exterior of the electromagnetic pump 20 of theembodiment. FIG. 3 shows a cross section A-A of the electromagnetic pump20 in FIG. 2. FIG. 4 shows how the electromagnetic pump 20 of theembodiment is incorporated into the valve body 80. As shown in thefigures, the side surface of the cylinder 42 of the electromagnetic pump20 is formed with an arc-shaped pin groove 44 at a position farther fromthe solenoid portion 30 than a position at which the discharge port 43is formed. In the electromagnetic pump 20 of the embodiment, the pumpportion 40 is inserted into the valve body 80 with the solenoid portion30 exposed, and a pin 84 is passed through a pin hole 82 formed in thevalve body 80 such that the pin 84 engages with the pin groove 44 insidethe valve body 80 to fix the pump portion 40 to the valve body 80. Thefollowing assumes that the pin groove 44 is formed at a position on thecylinder 42 closer to the solenoid portion 30 than a position at whichthe discharge port 43 is formed. Since the discharge port 43 is under ahigh pressure due to the operation of the electromagnetic pump 20, thehydraulic oil tends to leak from the discharge port 43 to a gap betweenthe cylinder 42 and the valve body 80. The hydraulic oil leakage maytherefore reach the solenoid portion 30 side via the pin groove 44, andin such case, may result in a loss of hydraulic pressure. However, inthe embodiment, the pin groove 44 is formed at a position farther fromthe solenoid portion 30 than a position at which the discharge port 43is formed so that such a failure does not occur.

According to the electromagnetic pump 20 of the embodiment describedabove, the pump portion 40 is inserted into the valve body 80 with thesolenoid portion 30 exposed, and the pin 84 is passed through the pinhole 82 formed in the valve body 80 such that the pin 84 engages withthe pin groove 44 inside the valve body 80 to fix the electromagneticpump 20. The pin groove 44 is formed at a position farther from thesolenoid portion 30 than a position at which the discharge port 43 isformed. Therefore, even if the hydraulic oil leaks from the dischargeport 43 to the gap between the cylinder 42 and the valve body 80, thehydraulic oil is much less likely to reach the solenoid portion 30 side,and a loss of hydraulic pressure can thus be prevented.

In the electromagnetic pump 20 of the embodiment, the intake check valve60 and the discharge check valve 70 are embedded inside the cylinder 42.However, one or both of the intake check valve 60 and the dischargecheck valve 70 may be disposed outside the cylinder 42.

The electromagnetic pump 20 of the embodiment is configured as a type ofelectromagnetic pump in which one reciprocal movement of the piston 50discharges the hydraulic oil twice from the discharge port 43. However,the present invention is not limited to this example. Theelectromagnetic pump 20 may be any type of electromagnetic pump providedthat the electromagnetic pump is capable of discharging the hydraulicoil in association with the reciprocal movement of the piston. Suchexamples include an electromagnetic pump that suctions the hydraulic oilthrough the intake port into the pump chamber when the piston isforwardly moved by the electromagnetic force from the solenoid portion,and discharges the hydraulic oil inside the pump chamber from thedischarge port when the piston is backwardly moved by the biasing forceof the spring, as well as an electromagnetic pump that suctions thehydraulic oil through the intake port into the pump chamber when thepiston is backwardly moved by the biasing force of the spring, anddischarges the hydraulic oil inside the pump chamber from the dischargeport when the piston is forwardly moved by the electromagnetic forcefrom the solenoid portion.

The electromagnetic pump 20 of the embodiment is used to supply ahydraulic pressure for turning on and off a clutch or a brake of anautomatic transmission mounted in an automobile. However, the presentinvention is not limited to this example, and the electromagnetic pump20 may be used in any system that transports fuel, transportslubricating fluid, or the like.

Here, the correspondence relation will be described between mainelements in the embodiment and main elements of the invention as listedin the Summary of the Invention. In the embodiment, the hydrauliccircuit that includes the valve body 80 corresponds to a “fluid pressurecircuit”; the cylinder 42 to a “cylinder”; the piston 50 to a “piston”;the solenoid portion 30 to an “electromagnetic portion”; and the pingroove 44 to a “pin groove”. Note that with regard to the correspondencerelation between the main elements of the embodiment and the mainelements of the invention as listed in the Summary of the Invention, theembodiment is only an example for giving a specific description of abest mode for carrying out the invention explained in the Summary of theInvention. This correspondence relation does not limit the elements ofthe invention as described in the Summary of the Invention. In otherwords, any interpretation of the invention described in the Summary ofthe Invention shall be based on the description therein; the embodimentis merely one specific example of the invention described in the Summaryof the Invention.

The above embodiment was used to describe a mode for carrying out thepresent invention. However, the present invention is not particularlylimited to such an example, and may obviously be carried out in variousembodiments without departing from the scope of the present invention.

The present invention may be used in the manufacturing industry of anelectromagnetic pump, and the like.

1. An electromagnetic pump comprising: a pump portion that includes acylinder that is formed with an intake port and a discharge port thatare in communication with a flow passage of a fluid pressure circuit, apin groove, and a piston that through a reciprocal movement inside thecylinder suctions a fluid from the intake port and discharges the fluidfrom the discharge port; and an electromagnetic portion thatreciprocates the piston, wherein inserting the pump portion inside thefluid pressure circuit with the electromagnetic portion externallyexposed from the fluid pressure circuit, and inserting a pin fromoutside into the pin groove incorporates the electromagnetic pump insidethe fluid pressure circuit, and the pin groove is formed at a positionfarther from an electromagnetic portion side than the discharge port. 2.The electromagnetic pump according to claim 1, wherein the intake portis formed on an end surface of the cylinder on a side opposite from theelectromagnetic portion side, the discharge port is formed in a sidesurface of the cylinder, and the pin groove is formed on the sidesurface of the cylinder.